Coated fabric and method of making the same

ABSTRACT

A coated fabric comprises a base ply of a fiber material such as a non-woven fiber material, for example, a polypropylene non-woven material, having a thermoplastic film, for example, an ethylene methyl acrylate film, bonded thereto. The base ply has densified and undensified portions thereof, the densified portions defining densified areas on a coating surface of the base ply, and the thermoplastic film is heat-bonded to the coating surface at least at the densified portions thereof. A method of making the coated fabric comprises contacting the thermoplastic film in heat-softened condition with the coating surface of the base ply, and allowing the film to cool.

This is a divisional of co-pending application Ser. No. 06/690,350 filedon Jan. 10, 1985 U.S. Pat. No. 4,753,840.

BACKGROUND OF THE INVENTION

The present invention is concerned with a thermoplastic film-coatedfabric, more particularly with a thermoplastic film-coated fibermaterial which is well suited for use in incontinence control garments,surgical gowns, sheets, dressings and the like as well as in femininehygiene products, and to a method for the manufacture of suchthermoplastic-coated fabrics.

The coating of thermoplastic films on fiber materials, includingnon-woven synthetic fiber materials, is known in the art. For example,U.S. Pat. No. 4,275,105 discloses a stablized absorbent rayon web whichmay constitute a continuous filament, spun-bonded web or an air-laid,wet-laid or carded web of rayon fibers of staple length or longer intowhich a thermoplastic web having open areas is melted from the bottomsurface thereof to a depth of about 10 to 40% of the depth of the web. Anumber of thermoplastic films including, among others, polyethylene,polypropylene, polyester and ethylene methyl acrylate are disclosed.

U.S. Pat. No. 4,367,112 discloses a biaxially oriented polypropylenefilm stated to exhibit improved heat-seal strength and good opticalclarity characterized by having on at least one surface thereof acontinuous coating of a copolymer of ethylene and methyl acrylate.Similarly, U.S. Pat. No. 4,076,895 discloses that ethylene acrylic acidcopolymers or ethylene-acrylic acid ester copolymers such asethylene/ethyl acrylate and ethylene/methyl acrylate may be used asextrusion coatings on transparent, polymeric webs such as orientedpolypropylene, cellophane, polyesters, nylon, etc. in order to imparttransparency to the multi-layered film resulting from the process. In asimilar vein, U.S. Pat. No. 4,416,937 discloses that a variety ofsomewhat polar synthetic thermoplastic polymers such as randomcopolymers of ethylene with acrylic or methacrylic acid are known toexhibit reasonably good adhesion to a variety of metallic andnonmetallic substrates.

SUMMARY OF THE INVENTION

In accordance with the claimed invention there is provided a coatedfabric comprising a base ply of a fiber material, preferably a non-wovenfabric, having densified and undensified portions thereof, the densifiedportions defining densified areas on at least one surface, designatedthe coating surface, of the base ply; and a thermoplastic filmheat-bonded to the coating surface at least at the densified areasthereof.

In one aspect of the invention, the fiber density of the densifiedportions of the base ply is at least about one and one-quarter timesgreater than that of the undensified portions of the base ply and thedensified portions define a repeating pattern of densified portions inthe base ply. The densified portions are preferably flush with orprotrude above the coating surface.

In another aspect of the invention, the fiber material comprises apolyolefin fiber material, preferably a polypropylene fiber material.The thermoplastic film may be selected from the group consisting ofpolymers of propylene, ethylene methyl acrylate, ethylene vinylacetate,ethylene, block copolymers of butadiene and styrene, ethylene ethylacrylate, ethylene methyl methacrylates, and compatible copolymers oftwo or more of the foregoing. The thermoplastic film is preferably anethylene acrylate film, more preferably an ethylene methyl acrylatefilm, and most preferably the latter is coated on a base ply comprisinga non-woven polypropylene fiber material.

Another aspect of the invention provides a coated fabric comprising: abase ply of non-woven polyolefin fiber material having densified andundensified portions thereof defining an interspersed pattern ofdensified and undensified areas on at least one surface, designated asthe coating surface, of the base ply; and a thermoplastic filmheat-bonded to the coating surface at least at the densified areasthereof, the depth of penetration of the film into the base ply beinglimited so that the thermoplastic film comprises a surface coating onthe coating surface of the base ply.

In another aspect of the invention the base ply may comprise fibers ofpolypropylene, polyethylene, polypropylene sheathed with polyethylene,polyesters, rayon, nylon and blends of two or more of the foregoing.

In accordance with the claimed invention there is also provided a methodof making a coated fabric comprising: heat-bonding a thermoplastic filmto a base ply of a fiber material, preferably a non-woven fibermaterial, the base ply having densified and undensified portions thereofand the densified portions extending to at least one surface, designatedthe coating surface, of the base ply; the heat-bonding being carried outby contacting a surface of the thermoplastic film in a heat-softenedcondition with the coating surface of the base ply, and allowing thefilm to cool.

One aspect of the invention includes maintaining the temperature of thethermoplastic film and the pressure of the contacting of the film andbase ply such that the depth of penetration of the film into the baseply is less than the depth of the base ply and forming the film into asurface coating on the coating surface of the base ply.

Another aspect of the invention includes the preliminary step of forminga pattern of densified and undensified portions in the base ply.

In a preferred aspect of the invention, the heat-softened film comprisesethylene methyl acrylate and is at a temperature of about 275° C. to315° C., preferably about 293° C. to 315° C., upon initial contact withthe base ply, which is preferably a non-woven polypropylene fabric.

Other aspects of the method of the invention include utilizing in themethod one or more of the materials described above as comprising thecoated fabric of the invention.

Still other aspects of the invention provide for a multi-plyincontinence garment wherein the outermost ply thereof comprises thefabric of the invention with the base ply thereof facing outwardly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The coated fabric of the present invention has utility in a number ofapplications including incontinence control garments, surgical gowns,sheets and dressings and feminine hygiene products. At least inpreferred embodiments of the invention, the coated fabric ischaracterized by being impervious or highly resistant to the passage ofliquid by virtue of its thermoplastic film coating while maintaining asoft cloth-like feel on the uncoated side of the base ply.

The base ply may comprise any suitable fiber material by which term ismeant any material made of fibers, whether woven or non-woven, althoughnon-woven fiber materials and in particular non-woven polyolefin fibermaterials have been found to have particular utility in the invention. Awide variety of other fibers such as rayon, nylon, polyester and thelike may be made into a utilizable fabric by any suitable technique. Forexample, spun-bonded or carded dry-laid or wet-laid non-woven fabricsmade from staple length or longer fibers may be utilized in theinvention. The fiber material comprising the base ply may obviouslycomprise a mixture not only of different length fibers but of fibers,whether of differing or identical length, which are made from two ormore dissimilar materials. For example, composite non-woven materials ofnylon-polyethylene, rayon-polypropylene or other suitable combinationsmay be employed. Non-woven fiber materials suitable for use in theinvention, including those made from polypropylene fibers, arecommercially available, relatively inexpensive and economicallywell-suited for use in disposable articles by which is meant articlesintended to be disposed after a single use rather than being launderedand reused. Some of these non-woven fiber materials have a softcloth-like feel which enhances the texture and appearance of garments orother articles made therefrom. Such non-woven fabrics are of courseliquid and vapor pervious due to their open construction.

In many applications such as incontinence control garments aliquid-impervious material is required to retain or prevent the passageof liquid such as urine or other physiological luids from passingtherethrough. Thermoplastic films such as polyolefin films, specificallyincluding polypropylene films, are well known for the purpose. Forexample, disposable diapers conventionally comprise a liquid permeabletop sheet, an intermediate absorbent pad or sheet and an outer or backsheet comprising a polypropylene film. While such constructions areuseful and have attained extremely wide-spread commercial acceptance, anesthetic drawback exists in that the polypropylene or otherthermoplastic film outer covering obviously lacks a cloth-like feel ortexture.

Aside from esthetics, it may be desired to adhere either a perforated orunperforated thermoplastic film to a fiber material such as a non-wovenpolyolefin fiber material. For example, as indicated by the aforesaidU.S. Pat. No. 4,275,105, a perforated thermoplastic film may be combinedwith a non-woven fiber material by melting the thermoplastic film intothe non-woven ply but to a depth less than the depth of the non-wovenply. One difficulty in attempting to coat a surface of a fiber material,in particular a low density non-woven fiber material, with athermoplastic film is that adhesion sufficiently strong to preventdelamination is often difficult to attain short of melting thethermoplastic film into the matrix of the non-woven fiber material asrequired by the aforesaid patent. Without wishing to be bound by anyparticular theory, it is surmised that the relatively low volume densityof fibers per unit volume of the fiber material (fibers plusinterstitial spaces between the fibers) provides relatively littlegripping or bonding area between the film and the fibers. This is aparticular problem when it is desired to bond the thermoplastic film toone surface only of the fiber material as opposed to melting the filminto the web of fiber material. Obviously, even when bonding athermoplastic film to a surface only of a fiber material there must besome degree of penetration by the thermoplastic film into the fibermaterial. However, when it is desired to retain on one side of thecoated fabric the texture and feel of the fiber material unpermeated bythe thermoplastic film, the fiber volume available to bonding by thethermoplastic film is necessarily limited. This can cause lack ofbonding or insufficient adhesion strength particularly whendifficult-to-bond combinations of film and fiber material are used.

It has now been discovered that adhesion strength between a giventhermoplastic film and a given fiber material, in prticular a non-wovenfiber material, can be greatly enhanced by providing densified portionsof the fiber material to which the thermoplastic film may be heat-bondedwith considerably greater strength of adhesion than that which isattainable between the thermoplastic film and the undensified portionsof the fiber material. It is believed that the greater volumeric densityof fibers per unit volume of fiber material in the densified areasprovides an enhanced total fiber surface area which can be contacted bythe thermoplastic film for a given depth of penetration and thereforeprovides greater adhesion strength. It is further believed, withoutwishing to be bound by any theoretical considerations, that the higherdensity of material in the densified portions of the fiber materialfacilitates heat transfer from the hot thermoplastic film beingheat-bonded and that this may induce a greater degree of softening offibers in the densified areas of the fiber material as compared to theundensified areas, or otherwise facilitate the bonding. Generally, theenhanced rate of heat transfer from the hot thermoplastic film to thedensified portions and consequent higher temperatures at the densifiedportions as compared to the undensified portions is believed to enhancebonding strength. The densified portions of non-woven fiber materialsare also believed to mechanically improve the tensile and tear strengthof such fabrics in addition to providing relatively smooth, dense andhigh surface areas for adhesion to the thermoplastic film. On the otherhand, the undensified portions of the fiber material (or "base ply" asit is sometimes referred to hereinbelow and in the claims) better retainthe feel, texture and flexural modulus of the uncoated base plymaterial. Therefore, the "hand", texture and flexibility of the coatedfabric can be selectively varied by varying both the size (surface areaon the coating surface of the base ply) of discrete densified andundensified areas and the proportion of densified to undensifiedportions of the base ply.

The densified portions of the fiber material may be formed in anysuitable manner. For example, a non-woven fiber material may simply beembossed to provide a desired pattern of densified portions. The baseply may be embossed by conventional embossing techniques, by beingpassed through the nip of a pair of rolls having a raised embossingpattern on one roll and a rubber coating on the other, pressure roll.Alternatively, one roll may be embossed with a raised pattern and theother roll may have a corresponding recessed pattern formed therein asis known in the art. Alternatively, any other suitable technique may beutilized such as calendar rolling and/or ultrasonic bonding to provide asuitable densification pattern in the fiber material. The densifiedportions formed in the non-woven fabric will normally extend throughoutthe depth thereof and appear on both surfaces of the fiber materialalthough one side of the fabric may have a negative configuration of thepattern appearing on the opposite side. For example, the fabric may havea pattern of densified portions formed therein by being embossed in awaffle-like pattern thereby providing a pattern of interspersedalternate densified and undensified areas. Obviously, any suitablepattern may be utilized including a diamond-like pattern, a checkerboardpattern, a striped pattern, an octagonal pattern, etc., so that theindividual densified and undensified areas may be square, rectangular,oval shaped, octagonal shaped, circular, etc. It is preferred that atleast one surface has a positive densified portion pattern and that thissurface be selected as the coating surface. By a positive pattern it ismeant that the densified areas are either flush with or raised above theplane of the coating surface and are not recessed below the plane.

The densified portions of the web provide areas of high adhesionstrength between the thermoplastic film and the non-woven fabric and itwill usually be desired to alternate rather small discrete areas ofdensified and undensified portions of the base ply. For example, thebase ply may be provided with discrete densified areas having a surfaceof about 1 to 8 square millimeters interspersed in an alternatingpattern with undensified areas of about 1/4 to 25 square millimeterseach. Individual densified surface areas resulting on the surface of thebase ply of non-woven fabric are preferably about 1 to 8 squaremillimeters each and may be separated from each other by lineardistances of about 1/2 to 5 millimeters, preferably from about 1/2 to 3millimeters. Consequently, assuming a square or rectangularcheckerboard-like pattern of densified and undensified areas, theundensified areas will measure about 1/4 to 25 square millimeters,preferably 1/4 to 9 square millimeters. These relative areas are alsopreferred for non-rectangular patterns. It has been found that thetexture of non-woven base ply materials can be selectively altered bychanging the relative size and proportion of densified and undensifiedareas. A fine pattern of densified and undensified areas provides adimpled appearance to the fabric and provides high adhesion strengthbetween the thermoplastic coating and the coating surface of the baseply, i.e., the surface to which the thermoplastic film is appliedwithout the necessity of melting the thermoplastic film largely orentirely into the depth of the non-woven fabric. Such melting of thethermoplastic film into the matrix provided by the non-woven fabricwould stiffen the latterand deprive it of its soft and cloth-like feelbecause the non-woven material would be filled with the smooth andrelatively rigid thermoplastic film.

A non-woven spun-bonded fabric suitable for use in the invention is spunfrom oscillating spinnerets whose relative speeds of oscillation,conveyor advance speed, fiber denier and filament count may be varied toproduce a wide variety of fabrics as is known in the art, e.g.,polypropylene non-woven fabrics. Another method of forming non-wovenfabrics utilizes short staple fibers of, e.g., polypropylene, having alength of about 1/4 to about 2 inches, preferably about 3/4 to about oneand one half inches and a denier of about 1.5 to 15, preferably about 3.A non-woven fabric may be made by a carded, dry-laid technique as wellknown in the art to produce a desired fabric weight. For example, anon-woven polypropylene fiber fabric having a fabric weight of fromabout 0.35 to about 2 ounces per square yard, for example, about 0.68ounces per square yard as determined by ASTM D-3376-79 may be prepared.The non-woven polypropylene fabric may have a thickness of about 6 to 12mils, preferably 9.5 mils, as determined in a manner similar to thatdescribed in ASTM D-1774-64.

The non-woven polypropylene fiber fabric as described above may bepattern-densified by embossing or other techniques to provide a patternof interspersed alternating densified and undensified areas. As usedherein and in the claims, the "densified" portions of the base ply aresimply those portions thereof which have been compacted or otherwisetreated to be reduced in thickness and consequently have a higherdensity of material per unit volume, usually by simply being physicallydeformation-compacted, as by embossing For example, a non-wovenpolypropylene fabric of 0.6 grams per cubic centimeter may havedensified portions of 0.9 grams per cubic centimeter.

The heat-bonding conditions must not be so severe as to melt thethermoplastic film substantially entirely into and through the fibermaterial of the base ply. Rather, the heat-bonding conditions oftemperature and contact pressure should be such as to coat the coatingsurface of the fiber material with the thermoplastic film with the depthof penetration of the thermoplastic film into the fiber material beinglimited to less than the entire depth of the fiber material, preferablyto less than one-half the depth of the fiber material.

A preferred thermoplastic film is one comprising or containing anethylene acrylate resin, and a preferred combination is a non-wovenpolypropylene fiber such as one described in detail above, to thecontact surface of which a thermoplastic film comprising or containingan ethylene acrylate component, preferably ethylene methyl acrylate, hasbeen heat-bonded. Ethylene methyl acrylate copolymers may comprise about5% to 80%, say 10% to 30%, methyl acrylate and 95% to 20%, say 90% to70%, ethylene.

In a preferred method of the invention, ethylene methyl acrylate isextruded at a screw temperature of about 275° to 315° C., preferably atemperature of at least about 293° C. in a film thickness which ispreferably from about 0.4 to 10 mils, more preferably about 0.4 to 2mils thickness. While still in a heat softened state, the extruded filmis stretched and brought into pressure contact with a base plycomprising a non-woven polypropylene fiber material, preferably one asdescribed in detail above, and the base ply and the thermoplastic filmare brought into pressure ccntact in the nip of opposed pressure rollswhich simultaneously cool and press together the thermoplastic film andthe base ply.

For example, the roll which directly contacts the thermoplastic film ispreferably water cooled to a temperature of about 25° to 80° F. (about-3.89° to 26.7° C.), preferably about 50° F. (about 10° C.). The cooledroll may be polished, matted or engraved to provide a desired texture tothe thermoplastic film. The opposing nip roll may have a rubber orrubber-like surface. A nip pressure of about 60 to 120 pounds per squareinch (about 4.22 to 8.44 kg per square cm), preferably about 80 poundsper square inch (about 5.62 kg per square cm) is utilized. In the caseof a non-woven polypropylene fiber base ply coated with a thermoplasticfilm comprising ethylene methyl acrylate, the melting temperature of thepolypropylene fiber is much higher than that of the thermoplastic filmso that thermal degradation of either the film or the fiber is not aproblem. If the extrusion temperature of the thermoplastic film isincreased beyond the limits indicated above and the materials aresubjected to the same contacting pressure, the thermoplastic film willflow entirely into the base ply resulting in a high adhesion compositeof the thermoplastic film embedded within the matrix provided by thenon-woven polypropylene fibers. However, the soft cloth-likecharacteristics of the uncoated side of the coated fabric of thisembodiment of the invention is lost and the result is a stiffer,plastic-like composite. If the extruder temperatures are significantlylower than those indicated, the heat-softened thermoplastic film willnot flow sufficiently around the fibers of the base ply resulting inpoor adhesion so that the base ply is readily pulled from thethermoplastic film. Within the indicated temperature rang,, highadhesion strength is attained between the thermoplastic film and atleast the densified portions of the base ply. Obviously, other extrusiontemperature ranges and bonding pressure ranges may be required or usefulfor other combinations of base ply and thermoplastic film.

In a preferred embodiment of the invention, the ethylene methyl acrylatecopolymer is extruded from a normally solid pellet hvving a specificgravity at 23° C. of at least about 0.94, and preferably of about 0.91to 0.97 as determined in a manner similar to that described in ASTMD-792. Conventional additives may be included in the thermoplastic film,for example, colorant pigments may be added to provide a desired colorthereto.

The non-woven base ply material comprises, in a preferred embodiment,polypropylene fibers laid in a fiber mat. The polypropylene fibers maybe prepared from a normally solid polypropylene pellet having a specificgravity of at least about 0.9 at 23° C., preferably from about 0.90 toabout 0.96 and a melt temperature of from about 160° to 172° C. Thenon-woven polypropylene fabric base ply preferably has a basis weight ofat least about 10 grams per square meter, for example, from about 10 to40 grams per square meter.

As mentioned above, the coated fabric in accordance with the inventionfinds utility in a large number of applications. For example, it may beutilized in any article in which it is desired to have aliquid-impervious ply which has on one side thereof a cloth-like feel.This makes it well suited for utilization, for example, in incontinencecontrol garments such as disposable diapers, training panties and thelike as well as in surgical gowns and sheets. The coated fabric of theinvention may be utilized in such garments with the thermoplastic coatedside facing the inside of the garment to provide a liquid barrier andthe uncoated side of the fiber material base ply facing the outside ofthe garment to provide a cloth-like feel and appearance thereto. Forexample, a disposable diaper or training panty may comprise an inner,liquid-pervious sheet, an intermediate absorbent pad or sheet and anouter backing sheet comprising the coated fabric of the invention placedwith the thermoplastic-coated side facing inwardly and the uncoated baseply facing outwardly.

While the invention has been described in detail with respect tospecific preferred embodiments thereof, it will be apparent to thoseskilled in the art upon a reading and understanding of the foregoingthat numerous alterations and modifications may be made thereto withoutdeparting from the spirit and scope of the invention and the appendedclaims.

What is claimed is:
 1. A method of making a coated fabriccomprising:providing a base ply of nonwoven fiber matrial, forming inthe base ply material a pattern of densified and undensified portions,the densified portions extending to at least one surface, designated thecoating surface, then providing a thermoplastic film in a heat-softenedcondition, contacting the heat-softened thermoplastic film with thecoating surface of the base ply, controlling the depth of penetration ofthe heat-softened thermoplastic film into the base ply to a depth lessthan the entire depth of the base ply by maintaining the temperature ofthe film and the contact pressure between the film and the base ply atpredetermined values, thereby forming the film into a surface coatingonly on the coating surface of the base ply, and therafter allowing thesurface coating of film the cool.
 2. The method of claim 1 wherein thebase ply comprises a non-woven fiber material.
 3. The method of claim 2including maintaining the temperature of the thermoplastic film and thepressure of the contacting of the film and base ply such that the depthof penetration of the film into the base ply is less than the depth ofthe base ply and forming the film into a surface coating on the coatingsurface of the base ply.
 4. The method of claim 2 including thepreliminary step of forming a pattern of densified and undensifiedportions in the base ply.
 5. The method of claim 1 wherein the base plycomprises a polyolefin fiber material.
 6. The method of claim 5 whereinthe base ply comprises a polypropylene fiber material.
 7. The method ofclaim 6 wherein the thermoplastic film is selected from the groupconsisting of polymers of propylene, ethylene methyl acrylate, ethylenevinylacetate, ethylene, block copolymers of butadiene and styrene,ethylene ethyl acrylate, ethylene methyl methacrylates, and compatiblecopolymers of two or more of the foregoing.
 8. The method of claim 6wherein the thermoplastic film comprises ethylene methyl acrylate. 9.The method of claim 1 wherein the base ply comprises fibers selectedfrom the group consisting of polypropylene, polyethylene, polypropylenesheathed with polyethylene, polyesters, rayon, nylon and blends of twoor more of the foregoing.
 10. The method of claim 9 wherein theheat-softened film is at a temperature of about 275° C. to 315° C. uponinitial contact with the base ply.
 11. The method of claim 10 whereinthe heat-softened film is at a temperature of at least about 293° C.